The proposed project concerns a new design for a novel, low-dose x-ray device for analyzer-based phase contrast imaging (ABI), a modality that uses x-ray refraction to produce dramatic improvements in imaging of the breast and other soft tissues. ABI has been well documented to produce extraordinary images at synchrotron facilities, but compact ABI prototypes have required imaging times that are far longer than what is practical for clinical use. We have developed a breakthrough approach, including a number of innovative design concepts that, when combined, are expected to deliver whole-breast imaging at 100 m resolution in 8.3 seconds. The goal of the proposed project will be to methodically design, optimize, and construct such an ABI system and evaluate its output in an expert reader study. ABI imaging offers many important potential benefits: 1) ABI has very high inherent soft-tissue image contrast due to the physics of x-ray refraction and strong scatter rejection, promising to provide clear visualization of calcifications and spiculations; 2) ABI can act as a planar-imaging method like mammography, but can also be used in tomosynthesis or computed tomography (CT) modes; 3) ABI has no need for injected contrast agent; 4) ABI may reduce radiation dose, because it can operate at higher x-ray energies (quasi- monochromatic at ~60keV); 5) the image detail seen in ABI may ultimately eliminate the need for tomosynthesis or CT, resulting in fewer images to be read in the clinic; 6) ABI may permit calcification types to be discriminated, thereby improving specificity; and 7) ABI permits quantitative imaging of tissue density. Based on a preliminary prototype device, we have established strong evidence of feasibility of clinically practical ABI performance. ABI system development is a complex hardware-software co-design process. The main elements in this process will define the project's specific aims as follows: 1. Design and construct a compact ABI imaging system to demonstrate practical imaging time. 2. Develop simulation and phantom tools. 3. Optimize image processing and iterative reconstruction methods. 4. Evaluate imaging system using ex vivo whole breast specimens and hybrid tissue phantoms.